Screw driver having a pivoted self-aligning bit



March 17, 1953 M. A. WEST 2,631,623

1 SCREW DRIVER HAVING A PIVOTED SELF-ALIGNING BIT Filed June 28, 1949 INVENTOR. MAX WE LL A. W EST ATTOR N EY Patented Mar. 17, 1953 SCREW DRIVER HAVING A PIVOTED SELF-ALIGNING BIT Maxwell A. West, Portland, Oreg., assignor to Challenger Screw & Tool Corporation, Portland, reg., a corporation of Oregon Application June 28, 1949, Serial No. 101,760

2 Claims.

This invention relates to driving or turning tools, and more specifically, to screw drivers, either power driven or manually operated, for use in driving certain different types of screws and the like, and, in particular, for the driving of the conventional type of s ngle-slotted screw.

While single-slotted screws, with the conventional slot extending diametrically across the head of the screw, are conventionally made with the side walls of the slot parallel and vertical, or substantially so, it is common as well as incorrect practice to drive them with a driver having a tapered tip. The result is that the tip of the driver frequently escapes from the screw slot and when this occurs, there is always the likelihood of the slot being marred or reamed. Furthermore,

since the widths of the slots vary for screws of different sizes, attempts to drive an ordinary screw with a driver which is either too large or too small is a further source of annoyance and of inefficient driving of common screws.

An object of the present invention is to provide an improved screw driving tool in which the tip or slot-engaging portion of the bit will not have any vertical taper, the slot-engaging faces both lying in vertical planes which would be parallel except for a slight lateral convergence, whereby the ordinary tendency for the driver to be thrust out of the recess is avoided.

Another object of this invention is to provide an improved screw driving tool with a bit which can be adjusted to conform in size to screw slots of the recesses of different widths, within a limited range, and thus secure a better and tighter fit of the bit in the slot.

A further object of the invention is to provide an improved'screw driving tool which will drive the screw satisfactorily and efiieiently even though the axis of the driving tool is not in alignment with the axis of the screw, this object being accomplished by providing a-driving tool with a shank and a bit in which a limited amount of universal action is possible between shank and bit. Certain other objects will appear and will be mentioned as the description of the invention proceeds and the manner in which these objects and advantages are attained with my invention will be pointed out in the description. In the description which follows reference is to be made to the accompanying drawings, in which:

'Fig. 1 is an elevation of my improved screw driver, the driver in this case being adapted for manual use, showing one form of adjustable and removable bit in the same and illustrating my screw driver in use with an ordinary single slotted screw;

Fig. 2 is a vertical medial section through the lower portion of the driver of Fig. 1, corresponding to line 2-2 of Fig. 1, but drawn to a larger scale;

Fig. 3 is a side elevation of the adjustable and removable bit member of Figs. 1 and 2;

Fig. 4 is a developed plan of the periphery of the screw bit of Figs. 1, 2 and 3;

Fig. 5 is a side elevation of one of the lateral spring members of the driver, the view being taken on line 55 of Fig. 2;

Fig. 6 is an elevation of a modified form in which the adjustable removable bit of the driving tool can be made;

Fig. 7 is an elevation of still another form in which the bit can be made, this particular modified form of bit being specifically adapted for use with certain improved recessed screws.

Referring first to Figs. 1 and 2, the manuallyoperated screw driver illustrated includes the customary handle portion I0 and a shank II, the lower portion 12 of which is preferably of slightly greater diameter than the upper or main body of the shank. The bottom end of the shank and of the lower portion I2 is bifurcated or slotted and a pin l3 extends across the slot and through the opposite walls thereof. The pin intersects the axis of the shank and is normal to the shank axis.

A disc-like bit, designated as a whole by the reference character l4, having a hole through its center, is mounted on the pin I3, and a pair of lateral spring members I5, I5 (see Fig. 2) are also mounted on the pin I3 at opposite sides of the disc-like bit It and are held under slight compression between the inside faces of the shank slot walls and the opposed faces of the bit respectively. These spring members are identical and one of them is shown in Fig. 5.

The pin 13 is secured in place in the slotted end of the shank in any suitable manner. For example, the ends of the pin, extending slightly beyondthe outside surface of the shank at opposite sides, may be peened. Removal of the pin, when the disc-like bit I4 is to be removed, can then be accomplished by filing the outer edge of one of the peened ends of the pin until the pin can be driven out from the shank slot walls from that end. Other ways of securing the pin I3 in the shank, while making it possible to remove the pin without too much difficulty will suggest themselves. The center hole through the disclike bit 14 is slightly larger. than the correspond- 3 ing diameter of the pin [3, as apparent from Fig. 2, and the reason for this will be explained presently.

The disc-like bit I4 (see Figs. 2 and 3) constitutes a novel and very important feature of the invention. In one embodiment of my invention the bit is in the shape of a regular polygon, for example in the shape of an octagon as illustrated in Fig. 3. The disc comprises a central, preferably circular, body portion it of uniform thickness, and an outer rim portion ll preferably having a constant circumferential taper. Thus, referring to Fig. 3, starting at a radial shoulder Hi (there being a corresponding identical shoulder on the opposite face of the rim portion, in the same place but not shown in Fig. 3), and following around in clockwise direction as viewed in Fig. 3, the thickness of the rim portion H increases constantly clockwise, reaching its maximum thickness at the top of the shoulder 18 and then immediately dropping to minimum thickness. The radial lines to the same peripheral point on the two opposite faces of the rim portion will, however, always be parallel. For example, the radial lines a, a, or the radial lines I), b in Fig. 2 will always be parallel. This circumferential taper in the rim portion is represented by the developed plan of Fig. 4.

The bit it, as apparent from Figs. 1 and 2, can be rotated, with slight effort, on the pin it. The spring members l5, l5 interposed between the slot walls and the faces of the circular body portion It of the bit, prevent free rotation of the bit l4 but enable the operator to rotate the bit by slight finger movement. The purpose of rotating the bit, as will now be evident, is to bring that section of the rim portion into position for use, and thus for insertion into a screw slot, which best fits the slot. Thus, assuming that the screw driver with the bit M as shown is to be used for driving ordinary single-slotted screws of a particular size, such as the screw it of Fig. 1, in which the screw slot extends diametrically across the head of the screw and which screw slot has the customary horizontal bottom and vertical side walls, the bit it is given a partial rotation by the finger of the operator until that section of the rim, for example the section having its outer edge at 253 (Fig. 3), which will have the best fit for the particular screw slot in question, will be in position for use. Then as the bit is pushed into the screw slot, the inserted section of the rim portion of the bit will have a fairly and desirably snug fit in the screw slot at least at one point. When a screw of a different size, and thus having a slot of difierent width, is to be driven, provided the range of screw sizes is not too great, a further turn of the bit brings the proper section of the rim portion of the bit into the driving position.

The spring members it as illustrated by Fig. 5, may be made in the form of fingered discs having alternate fingers such as 3i and 32 bent oppositely and adapted to have spring-like engagement at their extremities with the opposed faces of the walls of the shank slot and the bit body respectively.

As frequently happens, the axis of the driver shank may be slightly out of alignment with the axis of the screw which is being driven. With an ordinary rigid screw driver such a situation would cause difficulty. Since the center hole through the bit hi as previously mentioned, is of slightly greater diameter than the pin i3, it will be apparent from Fig. 2 that the driver shank 4 may be swung slightly out of parallelism with the faces of the circular body portion I6 of the bit, for example to an extent of 10 to one side or the other, while, of course, the bit at the same time can swing on the axial line of the pin i3. Thus in effect the bit and the shank of the driver are connected by means permitting a limited universal action. The spring members l5 actually perform two functions in that they tend to hold the faces of the bit parallel to the Walls of the shank slot and thus to keep the bit and shank in alignment in one directional plane, and at the same time the spring members i5 prevent the bit from rotating too freely in the shank slot.

However, the fact that the shank and the bit are rotatable with respect to each other makes it also possible to convert the driver even into a turning crank for the screw, for the shank could, under extreme conditions, be swung down to a position in which it extends at with respect to the screw axis, and nevertheless in such position the shank and screw driver can still operate to turn the screw.

While the outer peripheral faces of the disc-like bit extend in planes parallel to the axis of the disc-like bit, I consider it preferable also to make the two peripheral or longitudinal edges of each outer face with a narrow bevel, a indicated at 2| in Fig. 2. In the case of power driven drivers particularly, the beveling or rounding of such edges at the periphery reduces the tendency for the slot walls of the screw to become marred as the bit is inserted into, or removed from the screw slot. Also it maybe desirable to knurl the outer or peripheral faces of the disc-like bit slightly, not only to prevent slipping of the bit along the screw slot when in place in the screw, but also to present a better finger hold when the operator gives a partial rotation to the bit in order to adjust it for a particular screw.

Some screw slots, instead of being formed with the conventional straight horizonta1 bottom wall, have a slot which is longitudinally concaved along the bottom. For the slots of such screws a bit having a circular, instead of a polygonal form, enables the bit to get a better driving grip by being able to enter further into the screw slot. The modified bit shown in Fig. 6 illustrates such a bit, The bit 22 of 6, like the bit it, has a central body portion 23 of uniform thickness, and an outer rim portion 2 with the circumferential taper, corresponding to the circumferential taper on the rim portion ll of the bit l4, and the bit has a shoulder 25 on each face markin the change from maximum to minimum thickness in the rim portion.

Fig. 7 illustrates a further slightly modified form in which the rotatable disc-like bit of my driver may be made. In the bit 23 of Fig. '7, parts of the circumferentially-tapered rim portion have been cut away so as to leave four similar, spaced, syminetrically-arranged rim portion sections 27, 28, 29 and so of the same size and shape but of varying thicknesses. These rim sections or wings of the bit 2&3 are specifically adapted for use with certain recessed-head screws in which the recesses may consist of a single lot terminating short of the perimeter of the screw head, or in which the recess of the screw head is cruciform in shape, the end walls of the slots in either case sloping obliquely upwardly while the side walls are substantially vertical and parallel for a considerable distance up from the bottom of the recess. Examples of screws having such recesses will be found in U. S. Letters Patent No. 2,216,382,

issued October 11, 1940, and U. S. Letters Patent No. 2,296,887, issued September 29, 1942. While the screws described in these patents have cruciform recesses, it is possible to drive the screws with an ordinary screw (11" er, due mainly to the fact that the side walls of such recesses are substantially vertical for a considerable distance. With such improved recessed screws of this type, my screw driver with a bit formed substantially as illustrated by the bit can be used even more satisfactorily than an ordinary screw driver having the customarily tapered bearing surfaces.

Other modifications can also be made in the rotatable adjustable and removable bit in my improved screw driving tool and within the scope of this invention. The bits which I have illustrated are shown as preferred examples since these bits are especially suited for ordinary singleslotted screws and for certain improved types of recessed screws in which the walls of the slots are vertical to a substantial extent. My screw driver is however not intended for use with recessed screws in which the slot walls have a constant taper or slope throughout their extent, for even though the bit of my driver presents vertical faces against such slot walls, the slope or taper of the slot walls will nevertheless exert a strong tendency to thrust the bit out of the recess when turning torque is applied, which is the recognized difficulty with such screws. out of my invention it is essential that the engaging faces of the bit and screw slot walls shall be so arranged that a maximum bearing surface of the bit against the screw slot of the recess will be obtained which will be parallel, or substantially parallel, to the screw axis as far as is practical.

I-claim:

1. In a screw driver of the character described, a shank having a slotted end, a pin extending across the slot and through the slot walls substantially perpendicular to the slot walls and shank axis, a disc-like bit mounted in said shank slot, said pin passing through a central bore in said bit, said bore being of slightly greater diameter than said pin to permit of misalignment of said bit with respect to said shank, said bit having a rim portion adapted for entry into screw slots so as to enable said bit to be brought into In the proper carrying position for driving engagement with a screw, the corresponding radii of the opposite faces of said rim portion at any point on the periphery being parallel to each other, said rim portion formed with a circumferential taper, whereby different sections of said rim portion will be of varying thicknesses, and a disc-like fiat spring mounted on said pin between one side of said bit and the adjacent wall of said shank slot.

2. A screw driver of the character described ineluding a shank having a slotted end, a pin extending across the slot, a disc-like bit mounted in said shank slot, sale. bit having a rim portion adapted for entry into screw slots so as to enable said bit to be brought into position for driving engagement with a scr w, the corresponding radii of the opposite faces of said rim portion at any point on the periphery being parallel to each other, said rim portion formed with a circumferential taper, whereby uiil'erent sections of said rim portion will be of varying thicknesses, parts of said rim portion being cut away leaving rim sections of similar size but of different thicknesses, said pin extending through a central hole in said bit, the diameter of said hole being slightly greater than the diameter of said pin, and the spacing between the inside walls of said shank slot being greater than the greatest thickness of said disc-like bit, whereby to permit slight lateral swing of said bit out of parallelism with the shank axis, and a pair of disc-like fiat springs mounted on said pin between the sides of said disc-like bit and the adjacent walls of said shank slot respectively.

MAXWELL A. WEST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 70,923 Voorhees Nov. 12, 1867 279,917 Colvin June 2 6, 1883 866,594 Lunoe Sept. 17, 1907 1,249,394 Hess Dec. 11, 1917 1,314,012 Mowers Aug. 26, 1919 1,755,946 Altenbach Apr. 22, 1930 

